This project has explored approaches, methods, and concepts for assessing the clinical performance of laboratory tests. Focus has been on basic discrimination accuracy as reflected in clinical sensitivity and specificity and as represented by receiver operating characteristic (ROC) plots. ROC plotting and analysis has been applied to patient databases, especially involving the use if lipid and apolipoprotein parameters to identify subjects with clinically important coronary artery disease (CAD). Two such studies revealed that all of these parameters have only modest ability to discriminate between subjects with and without CAD. A tentative guideline for use by the clinical laboratory community in assessing clinical accuracy of tests has been developed and published through the National Committee for Clinical Laboratory Standards.